What is in this article?:
- Atrazine, pigweed issues on the minds of corn growers
- Protect the technology
• Atrazine is under the microscope again.
• Concerns also have arisen about atrazine resistance.
• In recent years, some growers have asked for recommendations on controlling Roundup Ready corn in a replant situation.
Atrazine worries and resistant pigweed problems are just a couple of the weed control issues on the minds of corn producers as they plant the 2011 crop.
“Atrazine is under the microscope again,” says Eric Prostko, University of Georgia weed scientist. “In 2009, EPA called for a new evaluation of atrazine, and that process is continuing today. There are some people who would love to take atrazine away from corn growers. If that ever happens, it would be devastating because it is the foundation of our weed control program in corn.”
Concerns also have arisen about atrazine resistance, says Prostko.
“A few years ago, I reported that we were finding instances of resistance to atrazine, specifically in Macon County, Ga., in areas that were predominately dairy where they were using quite of bit of atrazine in their rotations. We continue to survey in that area. We’ve found multiple resistance in some areas of Macon County, where there is resistance to glyphosate, the ALS herbicides and atrazine,” he says.
In recent years, says Prostko, some growers have asked for recommendations on controlling Roundup Ready corn in a replant situation.
“In the early spring, if we get a late frost, we get a lot of calls about replanting Roundup Ready corn. There are a few things you can do for controlling Roundup Ready corn in a replant situation. In trials, we made an application of SelectMax in one field and Gramoxone Inteon plus atrazine in another. Select Max has been shown to be one of our better treatments if you do have to replant in Roundup Ready corn,” he says.
One change growers may see this year is a change in how the herbicide Accent is marketed, he says. “Historically in Georgia, we have been a big user of Accent, and it has been good for the control of Texas millet or buffalo grass. At the corporate level, DuPont is positioning away from the Accent products and is developing a line of products called the Q Products. Whenever you see a Dupont product with the ‘Q’ in it, it means it contains a safener called isoxadifen.
“Instead of Accent, they’ll be promoting Steadfast Q. This is a combination product that contains Accent. With Steadfast, we’d use 1.5 ounces. At that rate, we don’t get as much of the Accent formulation in the treatment as we would with a regular application of Accent, which is two-thirds ounce. But after several years of testing the product, I don’t think we lose anything going from Accent to Steadfast Q.”
Many Georgia growers, says Prostko, have turned to LibertyLink crops in response to problems with glyphosate-resistant Palmer amaranth pigweed.
“Glufosinate or Ignite does give us another mode of action to control pigweed if you grow cotton. About 22 percent of our cotton this past year was treated with glufosinate. We can use it in LibertyLink corn and it can be effective against Palmer amaranth if treated in a timely fashion. You probably still want to tank-mix it with atrazine. It’s also good on other weeds such as Texas millet, morningglory and sicklepod.”
But, he adds, there are a few concerns with the use of Ignite. “We’re seeing in our research that you still need a residual herbicide in all crops that we’re growing. Depending on the density of the Palmer amaranth, one residual may not be enough. We may need two to give us that extended residual control.”